The invention addresses problems associated with the delivery and assembly of abutments screws into dental implants and related components using a conventional torque ratchet wrench. Most dental implants currently used are manufactured with a bore having an internal machine screw thread to accept and retain an abutment or prosthetic screw. However, due to the intrinsic nature of a thread design, if components are not assembled with the system's required tunctional torsional preload, the abutment or screw will loosen from the implant. Once loose, the abutment or screw is at risk of failure as all the functional loads end up being applied directly to the thread itself.
To prevent such thread attachment from coming loose, the prosthetic restoration is assembled into the implant with a torsional preload to resist the opening of the assembled joint during normal functional loading, i.e. chewing. This assembly is accomplished by using a torsional screw driver or wrench. As a means to regulate the applied preload of the assembled joint, the industry has developed several, spring actuated, mechanical break-a-way neck hand held torque wrenches. In addition to providing the assembled implant/prosthetic joint with the correct pre-load for eliminating joint separation, these break-a-way torque wrenches are used to prevent stripping or fracturing of the screw thread or overloading the implant during assembly.
Although these tools meet the stated functional requirements, continuous wear of the internal moving parts of the break-a-way head, due to their mechanical design, causes such tools to drift out of calibration over time and use. In fact, information accompanying most of the vailable tools state that the tools must be recalibrated at least once a year as part of the maintenance program for the tools. Since these tools use a mechanical spring to apply the desired application of torque, sterilizing the tools with steam autoclaving has lead to corrosive binding ot the break-a-way neck. Once locked, these wrenches are unable to control the application torque applying the preload. Furthermore, based on the predetermined application preload needed to prevent opening of the assembled implant/prosthesis joint, an uncontrolled variation in the application torque may lead to fracture or failure of the prosthesis. These conditions give rise to concerns for these tool's long term replacement costs, dependable function over time, sterility requirements and overall reliability.